sub my_sub {
   # do stuff
   eval { potential icky bit };
   if ($@) {
      return 0;
   } else {
      return $something_useful;
   }
}

# MAIN

unless ( $result = my_sub() ) {
   # use $@ to figure out what to do
}

##</code><code>##

unless ( $result = my_sub() ) {
   # handle error condition based on error var
}